BR112017024690B1 - WATER-RESISTANT SEALING MATERIAL, GASKET OR WATER-RESISTANT VALVE SEALING, AND, PROCESS FOR PRODUCTION OF A SEALING MATERIAL - Google Patents

Abstract

WATER-RESISTANT SEALING MATERIAL, GASKET OR WATER-RESISTANT VALVE SEALING, AND, PROCESS FOR PRODUCING A SEALING MATERIAL. A water resistant sealing material suitable as a gasket or valve seal is disclosed. The sealing material comprises chemically modified exfoliated vermiculite (CEV) in a proportion of 30-70% w/w sealing material and a filler in a proportion of 70-30% w/w sealing material, and optionally other additives in a proportion of 0-10% w/w of sealing material. Modified CEV comprises monovalent cations that enhance water resistance. The sealing material is particularly useful in providing improved water resistance in gaskets and valve seals.

Description

[001] The present invention relates to sealing material for gaskets and valve seals, more specifically, the present invention relates to a gasket and/or valve seal with improved water resistance.

[002] Chemically Exfoliated Vermiculite (CEV) is formed by treating vermiculite ore and swelling it in water. In one possible preparation method, the ore is treated with a saturated solution of sodium chloride to exchange the magnesium ions for sodium ions, and then with n-butyl ammonium chloride to replace the sodium ions with n- ions. butyl ammonium. Alternatively, the ore can be treated with a saturated solution of lithium citrate in a one-step process. In washing the treated ore with water, swelling occurs. The swollen material is then subjected to high shear to produce an aqueous suspension of very fine vermiculite particles (diameter below 50 μm). Other chemical treatment agents are known to those skilled in the art.

[003] US 4,219,609 describes the contact of pure exfoliated vermiculite with the steam of a concentrated solution of ammonia (or amine) in water. Ammonia dissociates in water to form ammonium hydroxide, but the dissociation constant of ammonia in water is 1.8 x 10-5 at 25°C. Therefore, the level of ammonium in the vapor or solution is very low. Example 1 examines the effect of steaming an ammonia solution in vermiculite exchanged for n-butyl ammonium, with exposure for 3 days. This method may involve bonding the amine to the clay surface over the solution.

[004] US5330843 relates to waterproofing an article of pure exfoliated vermiculite, such as a film, and application to gaskets. The method involves imparting a delaminated vermiculite article with a solution of a monovalent organic cation. Sodium is the preferred cation. Other materials may include composites, but examples thereof are paper and membranes in which pure vermiculite is present as a separate phase. No testing of the films is performed under load.

[005] GB1,016,385 describes that pure vermiculite films can be stabilized through exposure to polyvalent cationic solutions, examples used are magnesium chloride and aluminum chloride.

[006] It is known that chemically exfoliated vermiculite films that are composites of CEV and filler generally have lower water resistance than films made of CEV alone.

[007] Surprisingly, the inventors have found that the modified composite valve gaskets and seals according to the invention provide an improved water resistant film and sealing material.

[008] It is therefore an object of aspects of the present invention to provide gaskets, valve seals, sealing materials for gaskets or valve seals, gasket seal layers, valve compression rings and/or gasket sheets with strength to improved water.

[009] In accordance with a first aspect of the present invention, there is provided a water resistant sealing material comprising chemically exfoliated modified vermiculite (CEV) in a proportion of 30 to 70% w/w sealing material and a filler in a proportion of 30 to 70% w/w sealing material, and optionally other additives in a proportion of 0 to 10% w/w sealing material, wherein the modified CEV comprises monovalent cations which enhance water resistance.

[0010] The sealing material can be a dynamic or static sealing material. For example, the sealing material of the invention may be a valve sealing material or the sealing material may be a gasket sealing material.

[0011] Suitable applications for valve seals include valve stem seals such as valve stem oil seals.

[0012] It will be apparent from the foregoing aspects of the invention that the sealing material is a composite. The sealing material may be in the form of a sheet. Such sheets may be cut or molded into shapes suitable for use as a gasket or as a sealing layer of a gasket. Alternatively, the seal material/sheet can be formed into rings for use as valve compression rings. Suitably, the sheets may be cut and then pressure molded, such as molded in a die, into rings for use as valve compression rings. Therefore, in an embodiment of the first aspect, the invention extends to a sealing sheet of water resistant gasket composite or valve composite compression rings comprising chemically exfoliated modified vermiculite (CEV) in a proportion of 30 to 70 wt%. /p of foil or o-ring and a filler in a proportion of 30 to 70% w/w of foil or o-ring, and optionally other additives in a proportion of 0 to 10% w/w of foil or o-ring , wherein the modified CEV comprises the monovalent cations that enhance water resistance.

[0013] By monovalent cations that enhance the water resistance is meant the cations that improve the water resistance of the material, sheet, ring or sealing layer. Water resistance can be manifested by preventing the filler from softening and extruding the sealing material such as in a gasket/seal layer/sheet/valve seal or valve compression rings, which reduces the structural integrity of the same. . Monovalent cations that enhance water resistance can be introduced here by exchanging cations with cations, suitably other monovalent cations, in the unmodified CEV. It will be recognized that the monovalent cations which enhance water resistance are generally cations of an element of the periodic table or molecule other than the monovalent cations which are generally substituents on unmodified CEV such as lithium or n-butyl ammonium (C4H9NH3+). Therefore, monovalent cations that enhance water resistance are suitably more water resistance enhancers than a lithium cation, more suitably than a monovalent lithium cation and/or C4H9NH3+.

[0014] It will be recognized from the foregoing that the monovalent cations that enhance water resistance in the CEV are typically present at cation exchange sites in the CEV.

[0015] Suitably, in accordance with any aspect of the present invention, the monovalent cations that enhance water resistance are present in the CEV of the water resistant sealing material such as in a gasket/sheet/valve seal/ valve compression rings of the present invention at a higher level, typically at these cation exchange sites, than those in the unmodified CEV. Suitably, at least at a twofold level of magnification, more suitably, at an increase level of at least x10, more properly at a magnification level of at least x102, especially at a magnification level of at least x103. Since monovalent cations that enhance impermeability are typically present at cation exchange sites, these are exchangeable cations. Thus, monovalent cations that enhance impermeability in the sealing material such as in a gasket/foil/valve seal/valve packing seal layer of the present invention at cation exchange sites can be denoted as exchangeable cations. .

[0016] According to a second aspect of the present invention, there is provided a water resistant gasket comprising a sealing layer and optionally a core and/or backing for the sealing layer, the sealing layer comprising chemically exfoliated modified vermiculite (CEV). ) in a proportion of 30 to 70% w/w of sealing layer, and filler in a proportion of 30 to 70% w/w of sealing layer, and optionally other additives in a proportion of 0 to 10% w/w sealing layer, wherein the modified CEV comprises monovalent cations that enhance water resistance.

[0017] In accordance with a further aspect of the present invention there is provided a water resistant gasket or valve seal material comprising chemically exfoliated modified vermiculite (CEV) in a proportion of 30 to 70% w/w seal material and a filler in a proportion of 30 to 70% w/w sealing material, and optionally other additives in a proportion of 0 to 10% w/w sealing material, wherein the modified CEV comprises exchangeable monovalent cations that enhance strength the water.

[0018] According to a still further aspect of the present invention there is provided a water resistant gasket comprising a sealing layer and optionally a core and/or backing for the sealing layer, the sealing layer comprising chemically exfoliated modified vermiculite (CEV). ) in a proportion of 30 to 70% w/w of sealing layer, and filler in a proportion of 30 to 70% w/w of sealing layer, and optionally other additives in a proportion of 0 to 10% w/w of sealing layer, wherein the modified CEV comprises exchangeable monovalent cations that enhance water resistance.

[0019] According to a further aspect of the present invention there is provided a water resistant valve seal comprising the seal material comprising chemically exfoliated modified vermiculite (CEV) in a proportion of 30 to 70% w/w seal material, and filler in a proportion of 30 to 70% w/w of sealing material, and optionally other additives in a proportion of 0 to 10% w/w of sealing material, wherein the modified CEV comprises the monovalent cations which enhance the water resistance.

[0020] In accordance with a further aspect of the present invention, there is provided a water resistant valve seal comprising the seal material comprising chemically exfoliated modified vermiculite (CEV) in a proportion of 30 to 70% w/w seal material , and filler in a proportion of 30 to 70% w/w of sealing material, and optionally other additives in a proportion of 0 to 10% w/w of sealing material, wherein the modified CEV comprises the exchangeable monovalent cations that enhance water resistance.

[0021] The sealing material of the valve seal may be in the form of at least a first compression ring. Optionally, the valve seal can include other rings. The other rings may be set to the sealing material of the first ring or may be different.

[0022] It will be recognized that the term "ring" is a term known in the art and such rings may have any suitable central opening to accommodate a relevant movable part, such as a square or circular opening, preferably a circular opening.

[0023] The valve compression rings of the present invention may be continuous or split.

[0024] Valve seals can be used in association with rotating or reciprocating parts such as reciprocating stems or rotary ball valves. As such, the valve seal of any aspect of the present invention may be a valve vapor seal or a ball valve seal. Likewise, the valve seal material of any aspect of the present invention may be, for example, valve vapor seal material or ball valve seal material.

[0025] In use, the valve seals are placed in a stuffer box and subjected to tension by means of screws or the like. The load is commonly axial and this forces the seal to expand against the valve and the outside of the stuffer box, this creates the seal while allowing the valve to move.

[0026] Valve seals typically have multiple stacked layers or rings of seal material where each of the rings may have a particular function.

[0027] As such, according to a further aspect of the present invention the valve seal comprises two or more rings of the seal material, suitably at least three, four, five or six and/or up to fifteen, twelve, ten or eight rings of sealing material, wherein at least one of the rings of sealing material comprises the sealing material according to the present invention.

[0028] A valve ring of the seal material according to the present invention may preferably be used as the top and/or bottom ring of the valve seal. This may be preferable when, for example, temperatures are above the threshold for oxidation of graphite or oxidizing chemicals (such as NOx gases) are the medium.

[0029] Optionally, at least one of the other rings of sealing material in the valve seal of the present invention may comprise graphite. Graphite is more self-lubricating than vermiculite and can preferably be used in another intermediate ring between the valve rings in accordance with the present invention to help provide lubrication to the rotating or reciprocating component. When rings comprising sealing material according to the present invention are used as the top and/or bottom of the seal, these seals can protect the graphite layers from the medium or atmospheric oxygen, preventing their oxidation. The seal may comprise at least two other rings of gasket material comprising graphite, such as at least three, four or five, and/or the seal may comprise up to ten, eight or six layers of other gaskets comprising graphite.

[0030] O-rings and other packing material rings of the valve seal can be configured to be arranged co-axially, in use.

[0031] The seal of the present invention can be particularly useful when the valve seal is hydrotested before use. In this situation, the valve or valve/tube configuration is pressurized with high pressure water to control leakage before the medium is introduced. This hydrotest may soften or otherwise compromise the bottom seal if it is made of unmodified CEV-containing seal material.

[0032] Preferably, in accordance with any aspect of the present invention, at least 1%, more preferably at least 5%, even more preferably at least 10% of the exchangeable cations in the gasket/sealing layer/sealing material/ring or sheet are monovalent cations which increase impermeability, especially at least 25%, more especially at least 50%, for example 70 or 80 or 90 or about 100%.

[0033] Suitably, the water resistant gasket or valve/gasket/leaf/ring gasket/seal material is water resistant compared to a valve/gasket/leaf/valve seal/ring gasket or seal material which is the same as water resistant gasket or valve seal/gasket/leaf/valve seal/ring material except that it contains unmodified CEV, i.e. CEV that has not undergone cation-enhancing exchange with intensifying monovalent cations the water resistance after formation of the unmodified CEV material, as detailed above. Suitably, the gasket or valve seal material/gasket/leaf/valve seal/ring is water resistant compared to a gasket or valve seal material/gasket/foil/valve seal/ring which are the same gasket water resistant or valve seal/gasket/leaf/valve seal/ring material except that it contains non-exchangeable monovalent cations which enhance water resistance to an equivalent concentration level as exchangeable monovalent cations which enhance water resistance. Accordingly, an equivalent amount in both cases is the saturation of the CEV at that time. Accordingly, like the monovalent cations existing in unmodified CEV, lithium, n-propyl ammonium and n-butyl ammonium are not listed as water resistance enhancers or are listed as monovalent cations which do not enhance water resistance. Suitably, therefore, the monovalent cation which enhances the water resistance is other than lithium, n-propyl ammonium or n-butyl ammonium.

[0034] Typically, the monovalent cation that enhances the water resistance of any aspect is selected from at least one of an alkali metal, ammonium or a quaternary ammonium compound. The monovalent cations for substitution may more typically be selected from one or more of sodium, potassium, rubidium, cesium, francium, ammonium or a quaternary ammonium compound of the formula R4N+ wherein R is selected from methyl, ethyl or a combination thereof. Preferred monovalent cations that enhance water resistance in accordance with any aspect of the present invention are potassium, ammonium and sodium, more suitably potassium and ammonium, more suitably potassium.

[0035] Mixtures of two or more monovalent cations that enhance water resistance can be in any proportion. Suitable combinations of cations include K/Na, K/Rb and K/Cs. Typically, where a mixture of two cations is present, it is applied from solution in the range of 1:10 to 10:1 (mol.dm-3:mol.dm-3).

[0036] Preferably, the CEV and filler are intimately mixed and preferably each evenly distributed throughout the seal/layer/sheet/ring material so that they form a generally homogeneous mixture. As mentioned above, the monovalent cation that enhances water resistance can be introduced by exchanging cations with cations in the unmodified CEV. Exchange of monovalent cations is generally believed to occur on the surface and/or between vermiculite lamellae where the exchangeable cations of unmodified CEV are replaced by monovalent cations which enhance water resistance.

[0037] Typical levels of CEV in material, sheet, layer or gasket of any aspect are in the range of 30 to 68% w/w, more typically 35 to 65% w/w, even more typically 40 to 40% w/w. 60% w/w of material/sealing layer.

[0038] Typical filler levels in material, sheet, layer or gasket of any aspect are in the range of 32 to 70% w/w, more typically 35 to 65% w/w, even more typically 40 to 40% w/w. 60% w/w of material/sealing layer.

[0039] Optionally, additional additives may be present in the material, sheet, layer or gasket of any aspect in the range of 0 to 8% w/w, more typically 0 to 5% w/w, even more typically 0 at 3% w/w sealing material/layer.

[0040] It will be recognized that the combined level of CEV and filler will not exceed 100% w/w on the material, sheet, layer or gasket and may be 90% w/w in the presence of other additives so that the level selected in the above ranges must be properly matched.

[0041] Additional suitable additives may be selected from reinforcing agents such as crushed glass fiber or rubber.

[0042] The degree of cation exchange of the material/layer/sheet/seal ring depends on a few factors. However, although the exchange occurs in chemically exfoliated vermiculite, the filler may have the effect of creating platelet nano-spacing to maximize cation exchange in this way.

[0043] Typically the modified CEV is at least 70% cation exchanged with monovalent cation which enhances water resistance, more typically at least 80% cation exchanged, even more typically at least 90% cation exchanged, where 100% exchanged is considered to mean full saturation with the monovalent cation which enhances water resistance. However, increased water resistance is achieved at much lower levels of exchange, and therefore the modified CEV can be as low as at least 1% cation exchanged, e.g. at least 5 or 10 or 25 or 50% cation exchanged. monovalent altered cation that enhances water resistance. The shift to full saturation of the modified CEV can be determined by X-ray powder diffraction. For example, when an unmodified CEV sample saturated with lithium ions is treated with a solution of cations that enhance water resistance, such as cations that enhance water resistance, substitution of lithium cations in X-ray diffraction in CEV powder can be used to show the replacement of a peak corresponding to lithium cations and their layer spacing with a second peak corresponding to the cations that enhance water resistance and their layer spacing.

[0044] By “full saturation” is meant that the unmodified CEV cations present at the monovalent cation exchange sites, typically the exchange sites between vermiculite lamellae, are almost completely exchanged for the cations that enhance resistance to Water. It will be evident that as a result of, for example, mechanical blockages, differences in temperature, pressure, etc., full exchange by monovalent cations that enhance water resistance at the monovalent cation exchange sites may not be possible. As such, suitably, almost completely exchanged may be at least 95% exchanged, such as at least 96%, 97%, 98%, 99% or at least 99.5% exchanged. During the preparation of unmodified CEV, a large excess of exfoliating cations such as lithium or n-butyl cations is generally used. This excess is expected to cause substantially all of the available monovalent cation exchange sites of vermiculite to be occupied in the CEV. As such, the definition of "total saturation" provided above will also generally mean that at least 90%, such as at least 95%, 97%, 98%, 99%, 99.5%, or substantially all of the cation exchange sites monovalents available in the CEV are occupied by cations that enhance water resistance.

[0045] The gasket can be multi-layer or single-layer. In the case of a single layer gasket, the sealing material or layer is molded to form the entire gasket whereas in a multilayer gasket which may have two or more layers, the sealing material may form one or more layers. of the gasket and the core and/or support can form other layers. In one embodiment, the gasket is in the form of a core interposed between two sealing layers which are generally typically, but not necessarily, contiguous therewith. Such a gasket is typically formed to be interposed between the contacting surfaces of contacting parts to thereby provide a seal therebetween. In one embodiment, the gasket may be in the form of a backing layer and a sealing layer thereon which is typically but not necessarily generally contiguous therewith. The gasket can be in the form of a laminate or the backing layer can be interpenetrated by the sealing layer. Such interpenetration can be affected, for example by a gauze or wire mesh backing interpenetrated by the sealing layer to thereby reinforce the sealing layer.

[0046] In an additional embodiment of a multilayer gasket, other layers may be applied to the sealing layer, for example, the sealing layer may have another layer or coating interposed between the sealing layer and the respective mating surface, in use. Such other layers are known to the skilled artisan and depend on the application in which the gasket is to be used.

[0047] Therefore, it will be recognized that the gasket sealing material or layer may be used in any suitable gasket application. Typical embodiments include: kammprofile type, spiral wound, steel core gaskets that can benefit from the enhanced water resistance of the sealing material of the present invention.

[0048] Advantageously, a seal material or gasket or valve seal or seal sheet of the present invention provides improved water resistance. Without being bound by any theory, evidence suggests that merely communicating a CEV filler-free gasket/ring material or layer with a relevant cation in the form of a cationic solution can reach saturation more slowly than a gasket layer/ring or material with filler according to the invention. Therefore, sealing layers/rings or materials including filler according to the invention are able to be exchanged more efficiently than filler-free sealing materials. Surprisingly, this has led to enhanced water resistance in such materials.

[0049] In accordance with any aspect of the present invention, the material/layer/sheet/sealing ring are exchanged into cations through contact with the monovalent cation which enhances water resistance, typically by contacting the material/layer/sheet /seal ring having unmodified CEV with a solution of the relevant monovalent cation.

[0050] In some embodiments, the monovalent cation that enhances water resistance is introduced to the material/layer/sheet/seal having unmodified CEV as a citrate or chloride salt, typically a solution thereof, preferably as a salt. of citrate.

[0051] Preferably, the fillers of any aspect of the present invention are inert fillers. By inert fillers is meant not effective as a binder in the gaskets or value seals or sealing materials of the present invention and/or generally chemically inert in the gasket or value seals applications of the invention. Suitably, the fillers are non-hygroscopic, non-reactive with water and/or non-reinforcing.

[0052] Suitable inert fillers are of the plate or particulate filler type known to those skilled in the art. Plate-type filler in the context of the present invention means fillers that adopt plate-like, layered or sheet-like structures in the sealing material. Plate-type fillers include talc, other forms of vermiculite and mica. Other forms of vermiculite include thermally exfoliated vermiculite. Suitable particulate fillers include amorphous silica, quartz silica and calcium carbonate.

[0053] It has been found that the introduction of a plate-type or particulate filler to the CEV to form a film, typically one intimately mixed with it, provides enhanced water resistance, improving the exchange of monovalent cations in contact with them, suitably a solution of the same.

[0054] Typically, the average particle size d50 of the filler as, for example, determined by diffraction of light with a Malvern Mastersizer is in the range of 10 nm to 50 μm, more preferably, from 50 nm to 30 μm, even more preferably from 500 nm to 25 μm.

[0055] Typically, the average particle size d50 of the CEV, as, for example, determined by diffraction of light with a Malvern Mastersizer is in the range 1 μm to 100 μm, more preferably from 5 μm to 50 μm, even more preferably from 10 μm to 30 μm.

[0056] The surface area of the filler as determined by nitrogen absorption such as ISO 9277 is less than 200 m2/g, more preferably less than 10 m2/g, even more preferably less than 5 m2/g.

[0057] Under ambient conditions the spacing d (clay-clay layer spacing) of the CEV in the sealing material or gasket sealing material of the present invention as determined by X-ray diffraction suitably lies within the range of 10 to 12 Â, as can be adequately measured by a PANalytical XPert MPD theta-theta diffractometer, using Cu Kα radiation (X = 1.5418 Â), calibrated using a Si standard and equipped with a Ni filter and curved graphite monochromator in the beam subjected to diffraction, and operating in the Bragg-Brentano reflection geometry. A 1 cm x 1 cm square of the sample was illuminated using programmable divergence and anti-scatter slits. The X-ray tube was operated at 40 kV and 40 mA.

[0058] It will be recognized that two or more of the optional features of any aspect of the invention may be combined with any aspect of the invention mutatis mutandis.

[0059] In accordance with a third aspect of the present invention, there is provided a process for producing a valve or gasket sealing material comprising the steps of: a) mixing the chemically exfoliated vermiculite (CEV) with a filler to form an intimate mixture of the same; b) optionally forming a sheet from the mixture; c) optionally drying said sheet formed from the mixture; and d) exchanging the mixture/sheet/dry sheet into monovalent cations by contacting them with a solution of a monovalent cation that enhances water resistance.

[0060] Suitably, the CEV can be formed by treating the vermiculite ore with lithium citrate solution followed by washing the treated ore. Treatment with other cations is also possible. Suitably, however, the vermiculite ore is treated with lithium citrate. As such, the CEV of step a) may be at least partially, and preferably completely, saturated with the treating cation. The treating cation can be any suitable cation, but is typically lithium, n-butyl ammonium ((n-butyl)NH3+), or n-propyl ammonium ((n-propyl)NH3+), more typically, lithium. A pre-treatment step of the vermiculite ore with sodium is typically required when (n-butyl) NH3+ or (n-propyl) NH3+ are used as the treatment cation.

[0061] Accordingly, the effect of contacting step d) is to cause the monovalent cations that enhance water resistance to be present in the water resistant valve CEV or gasket seal material at a higher level than that found in unmodified CEV, typically at cation exchange sites. Suitably, the monovalent cations that enhance water resistance are present at at least a twofold increase level, more suitably at an increase level of at least x10, more suitably at an increase level of at least x102, especially at a magnification level of at least x103.

[0062] Alternatively, monovalent exchangeable cations that enhance impermeability are present in the range 1x10 -5 to 5x10 -2 moles g -1 , more preferably 1x10 -4 to 1 x 10 -2 moles g -1 , even more preferably, 2 x 10-4 to 5 x 10-3 moles g-1 of sealing material. Cation exchange and chemical analysis can determine the amount of exchangeable cations in total and of a particular type in the materials, sheets or gaskets according to the invention. Such techniques are well known to the skilled artisan and can determine the cation exchange capacity (CEC) of the material, i.e., the amount of exchangeable cations. As detailed above, preferably, in accordance with any aspect of the present invention, at least 1%, more preferably at least 5%, e.g. 10%, of the exchangeable cations in the gasket/layer/sealing material/sealing sheet/gasket material valve seal or ring are monovalent cations which increase the impermeability, especially at least 25%, more especially at least 50%, for example at least 70 or 80 or 90 or 100%.

[0063] Preferably, after mixing the CEV, typically wet CEV in slurry form, although the CEV in dry powder form can be added to increase the CEV content, and the filler, intimate mixture is formed into a sheet and at least partially dried prior to cation exchange. Optionally, a gasket seal or valve ring layer is formed from the foil and even more optionally, this can be incorporated into a gasket or valve seal prior to cation exchange. Optionally, the valve ring is formed from the sheet by press forming, such as die forming. As such, optionally, step d) is the exchange of monovalent cations from the gasket seal layer or valve seal material by contacting them with a solution of a monovalent cation which enhances water resistance before or after incorporation. of the layer/sealing material in a valve gasket/seal.

[0064] Cation exchange is preferably accomplished by communicating the seal material, sheet or gasket/gasket seal layer or valve seal material/compaction rings with a solution of the relevant cation, typically an aqueous solution thereof .

[0065] The monovalent cation that enhances impermeability by communicating the material, sheet or gasket/valve seal material to be subjected to cation exchange is typically in excess of that stoichiometrically required to exchange all cation exchange sites, i.e. , at least 95%, more typically approximately 100%.

[0066] Preferred exposure times for contacting the material, sheet or gasket/valve seal material with a solution of the monovalent cation that enhances impermeability are 1 to 180 minutes, more preferably 5 to 180 minutes, plus preferably from 15 to 60 minutes, for example at least 2 minutes, more typically at least 10 minutes, even more preferably at least 20 minutes.

[0067] Suitably, the material, sheet or gasket/gasket seal layer or valve seal material/compaction rings are communicated with a solution of the relevant cation through immersion of the material, sheet or gasket/gasket seal layer or valve sealing material/compacting rings in the solution, preferably by immersing the material, sheet or gasket/gasket sealing layer or valve sealing material/compacting rings in the solution. Optionally, the solution is applied to the material, sheet or gasket/gasket sealing layer or valve sealing material/compaction rings by coating the solution onto the material, sheet or gasket/gasket sealing layer or valve sealing material. valve/compaction rings, typically followed by rinsing with deionized water. This method of application may be advantageous for valve sheets or gaskets/seals where immersion would not be commercially viable.

[0068] Advantageously, it has been found that replacing the sheet, typically dry sheet, with a cationic solution is more effective in producing a flexible sheet with improved water resistance than adding a cation exchange solution directly to the wet CEV mixture. /unmodified dry and filler before forming. In such cases, subsequent sheets have been found to be too sensitive for most applications.

[0069] Furthermore, the inventors have found that adding the cationic solution to unmodified wet/dry CEV prior to filler addition does not lead to effective sheet formation.

[0070] It will be recognized that two or more of the optional features of any aspect of the invention or of the first and/or second and/or third and/or other aspects may be combined with any aspect of the invention or the first and/or second and/or or third and/or other aspects mutatis mutandis.

[0071] Preferably, the sealing material, sheet or layer/ring according to any of the aspects presented herein may be compacted and such compaction may be carried out prior to use or prior to cationic replacement. Alternatively, compaction may occur during formation, such as cutting, of the sheet. Compression potentially increases sheet integrity and improves performance. Typically, the density of the uncompacted sheet or layer/ring is from 0.9 g/cm 3 to 1.5 g/cm 3 ; more preferably from 1.0 g/cm3 to 1.4 g/cm3 , more preferably from 1.1 g/cm3 to 1.3 g/cm3 . Suitable packing pressures for the gaskets will result in a sheet or layer/ring density in the range 1.0 to 2.1 g/cm3, more preferably 1.2 g/cm3 to 2.0 g/cm3, even more preferably from 1.6 g/cm3 to 1.9 g/cm3. Suitably, compaction pressures for valve seal materials/compacting rings may result in a sheet or layer/ring density in the range of 1.1 to 2.7 g/cm3, more preferably 1.3 to 2, 5 g/cm 3 , even more preferably 1.6 to 2.2 g/cm 3 .

[0072] The concentration of the cation in the monovalent cationic solution is not particularly limited, but can be in the range of 0.1 to 10 mol.dm-3, more preferably, in the range 0.5 to 5 mol.dm-3, still more preferably, in the range of 1 to 3 mol.dm-3. Generally, the cation is fully solvated and any concentration up to a saturated solution can be used for the cation exchange step.

[0073] In embodiments where the cationic solution is coated onto the sealing material, sheet or layer/ring, the concentration of the cation in the monovalent cationic solution is generally higher than for immersion application methods. Typically, when the cationic solution is coated onto the sealing material, sheet or layer/ring, the concentration of the cation in the monovalent solution is in the range of 1 mol.dm-3 to 10 mol.dm-3 such as 5 mol.dm-3 3 to 10 mol.dm-3, more preferably from 7 mol.dm-3 to 10 mol.dm-3 even more preferably from 8 mol.dm-3 to 9.5 mol.dm-3

[0074] Suitably, according to the present invention, the gasket/sheet/sealing layer/sealing material/compaction rings can be immersed in a solution of 0.2 to 3.0 mol.dm-3 for a period between 5 to 180 minutes, more preferably a 0.3 to 1.0 mol.dm-3 solution for a period of between 15 to 60 minutes.

[0075] Valve seal material can be treated by contacting a solution of a monovalent cation which enhances water resistance when positioned around a valve. Therefore, optionally, in step (d) the solution of monovalent cations that enhance the water resistance can be communicated with the valve seal materials when they are positioned around the valve. Suitably, in such an embodiment, the sealing material is not compressed to its target density prior to contacting the solution. Seals can be fully densified after treatment.

[0076] A significant increase in water resistance can be shown by weighing the treated and untreated seals after immersion in water.

Definitions

[0077] Where values are provided herein in % w/w, these are based on dry weight unless otherwise indicated. Where values are given as a percentage of cations, these are on a numerical or molar basis.

[0078] It will be recognized that the sheets, layers and sealing material contained herein in connection with valve seals are generally synonymous with the rings or compression rings of such seals. However, this does not exclude the possibility that a single compression ring may have multiple layers or be produced from multiple sheets.

[0079] For a better understanding of the invention, and to show how modalities thereof may be carried out, reference will now be made, by way of example only, to the following examples and figures in which: Figure 1 is a test device of bundles.

Examples Method

[0080] Example sheets were prepared from the dough composition formulations described in Table 1 by mixing the components to form a wet dough and then pulling a scraper blade in a molding direction through the wet dough to spread. an even coating over a backing layer (140 gsm paper, Cresta “D”). The coating was dried and the backing layer was removed by peeling the dry coating. The dried coating was cut with the longest dimension parallel to the molding direction (“with” grain) on a sheet of 5 cm x 2 cm test samples. Samples for the Gas Leak Test (DIN) at 90 mm OD x 50 mm ID were also cut.

[0081] Due to the varying viscosities of the mixtures, deionized water had to be added to the initial dough formulations to obtain a consistency that was molded into sheets. These water additions are shown in Table 1. After mixing and shaping into sheets, the sheets were consolidated, unless otherwise noted, to approximately 0.6 mm thick when dry, before cutting the test samples as described above. Specific thicknesses and densities are recorded in Table 1. Table 1: Composition of Test Sheets before Exchange

[0082] The summarized data for the fillers used are given in Table 2. Table 2: Filler data

[0083] The test film cut samples of the above formulations were then subjected to cation exchange by immersion in saline solutions 1 to 4 or spiral joints were immersed in saline solutions 5 and 6. 1. “Control” (untreated samples) 2. Samples first immersed in 0.33M Potassium Citrate (1N K+) before washing twice in deionized water and drying at 40°C for 3 hours. 3. As 2) with 1 M of Potassium Chloride (1 N of K+) 4. As 3) with 1 M of Sodium Chloride (1 N of Na+) 5. 0.33M of Cesium Citrate, procedure detailed below 6 1.0M Ammonium Citrate, procedure detailed below

[0084] Immersion (Beam) tests were performed on test samples treated according to conditions 1 to 4 above using the device illustrated in Figure 1.

[0085] A frame 2 for the dip beam test was constructed from a 16 mm square section PVC conduit. A pair of spaced opposite conduits 4,6 were arranged in a parallel fashion with a second identical pair 8, 10 superimposed on the first pair so as to leave a gap 22 therebetween to accommodate and hold a test sample 14 extending perpendicularly between them. the sets of overlapping conduits so that the ends thereof are clamped between the first 4, 8 and second 6, 10 overlapping conduits. The test sample 14 thus bridges the opening 12 between the set of overlapping conduits. A glass plate weight (360 g) 24 is resting on the respective second conduits 8, 10 to thereby prevent the test sample from moving during testing. Test sample 14 and frame 2 are designed to support 1 cm at each end of the test sample, leaving 3 cm of unsupported bridging space 12 between the conduits. A £1 coin (9.5 g weight, 22.5 mm diameter; 3.15 mm thickness) 16 was rested in the center of each test sample. For testing, frame 2 was placed in a clear polypropylene container 18. The test samples were all mounted so that the surface exposed to air during molding was facing downwards.

[0086] The container was filled with 1 L of deionized water 20 in order to submerge the test samples and the test samples were continuously observed for 1 to 2 hours and at subsequent intervals for 24 hours.

[0087] At 8 and 24 hours, the deterioration of test samples that did not collapse was assessed by measuring the downstream bending of the test samples in mm from the horizontal at the eye using a square with graduations in mm . The time taken for each test sample to collapse was recorded where appropriate._

Results Control:

[0088] In table 3 below, the comparative example numbers combine with the respective preparative example numbers in table 1, except comparative preparative example 1 which is designated comparative example 11 while the times to collapse in the beam test are data in minutes:seconds Table 3: Control Test Results

[0089] The 100% CEV samples, Comparative Example 11, lasted considerably longer than the samples containing a filler (Comparative Examples 1 to 10). The consolidated sample of Comparative Example 1 lasted longer than the unconsolidated sample of Comparative Example 2. 0.33 M (1 N) Potassium Citrate

[0090] In table 4 below, the examples produced by saline immersion 2 above are shown as examples 1 to 10 and Comparative Example 12. The numbers of examples 1 to 10 equate to the respective preparative numbers of table 1, except for the comparative preparative example 1 which is designated Comparative Example 12.

[0091] In table 4, the times to collapse in the beam test are given in minutes. However, all samples except the 100% CEV from Comparative Example 12 remained intact after 48 hours; the vertical bending (in mm) of the beams is recorded after 8 hours, after 24 hours, and after 48 hours.Table 4: Potassium Citrate Test Results

1 M (1 N) of Potassium Chloride

[0092] In table 5 below, examples produced by immersion in saline solution 3 above are shown as examples 11 to 20 and Comparative Example 13. Examples 11 to 20 use preparative examples 1 to 10 respectively. Comparative Example 13 uses Comparative Preparative Example 1.Table 5: Potassium Chloride Test Results

[0093] Comparative Example 13, containing Comparative Preparative Example 1 was again the only sample to break and this occurred between 8 and 24 hours.

1 M (1 N) of Sodium Chloride

[0094] In table 6 below, examples produced by immersion in saline solution 4 above are shown as examples 21 to 29 and Comparative Example 14. Examples 21 to 29 use preparative examples 1 to 9, respectively. Comparative Example 14 uses Comparative Preparative Example 1.Table 6: Sodium Chloride Test Results

[0095] Again, Comparative Example 14 breaks between 8 and 24 hours as for solution 3. The remaining samples flexed more than the corresponding examples for solution 3.

0.33M Cesium Citrate

[0096] Cesium citrate was prepared at a concentration of 0.33M by slowly dissolving 66 g of cesium carbonate in a deionized water solution of 42 g of citric acid monohydrate (both from Sigma Aldrich). The solution was made up to 400 ml before use, and allowed to stand for 24 hours to allow excess carbon dioxide to dissipate from the solution. In example 30 a spiral wound gasket containing a sealing layer formed from preparative example 3 was immersed in the cationic solution for 1 hour, washed, dried and tested by immersion in water for 30 minutes.

[0097] The water resistance of a gasket seal layer prevents the filler from softening and extruding from the gasket, which reduces the structural integrity of the gasket. In a control sample that was not subjected to cation exchange, after 30 minutes of immersion in water most of the filler was extruded. However, in example 30, there was no visual extrusion of the filler.

1M Ammonium Citrate

[0098] Ammonium citrate was formed at a concentration of 1M by slowly adding 58 g of ammonium carbonate (from Sigma Aldrich) to 84 g of citric acid monohydrate in deionized water and preparing to 400 ml. A 0.33M solution was formed by dividing these amounts into two equal parts in a total solution of 600 ml. In both cases, the solutions were left for 24 hours before use to dissipate carbon dioxide.

[0099] In example 31, a spiral wound gasket containing a sealing layer formed from preparative example 3 was immersed in the solution at a concentration of 1M for 1 hour, washed, dried and tested by immersion in water for 30 minutes.

[00100] In example 32, a spiral wound gasket containing a sealing layer formed from preparative example 3 was immersed in the solution at a concentration of 0.33M for 1 hour, lacquered, dried and tested by immersion in water for 30 minutes.

[00101] The gaskets of both example 31 and example 32 provided advantageous levels of waterproofing to the gaskets considering that there was no visual extrusion of the filler.

Leak Test

[00102] Modified SHELL gas leak tests were performed on gaskets containing a treated sheet formed according to Preparative Example 1 or Preparative Example 3 and using various cationic solutions.

[00103] All SHELL tests were performed on 4” (10.16 cm) Class 300 gaskets (per ANSI B16.5) having a 316L wire and containing the treated sheet.

[00104] The test rig had a weld neck flange with a raised face. The test volume of the equipment was approximately 2.0 liters. The following materials were used: Flanges: ASTM A 182 Gr. F11 or F12 Tube: ASTM A 335 P11 Screws: ASTM A 193 Gr. B16 Nuts: ASTM A 194 Gr. 4H

[00105] The flange face roughness was subjected to a smooth finish (Ra 3.2 to 6.3μm). All sample gaskets were dried for 1 hour at 100°C prior to testing.

[00106] To test the gaskets at room temperature, an initial bolt pressure of 290 MPa (i.e. 71 MPa in the pressed area of kammprofile, 107 MPa in the pressed area of the spiral wound gasket with inner and outer rings) was applied and the internal pressure rose to 5.2 MPa. After setting a time of 30 minutes, the pressure was held for 1 hour, after which the internal pressure was recorded.

[00107] To test the gaskets at an elevated temperature, an initial bolt pressure of 290 MPa (i.e., 71 MPa in the pressed area of kammprofile, 107 MPa in the pressed area of spiral gasket) was applied and the gasket containing the test was heated at a rate of about 100°C/h to 450°C. When the temperature reached 450°C the internal pressure was raised to about 3.4 MPa. The temperature was maintained for 1 hour after the internal pressure was recorded. The gasket was then allowed to cool to room temperature before the heating cycle was repeated.

[00108] The results of the SHELL tests are shown in Table 7 below. No additional gas was applied during the test. Table 7 - Gas Leak Test Results

[00109] Table 7 shows that the spiral wound gasket containing the sealing material has a better performance in performing gas leakage than the untreated sample whether consolidated or unconsolidated. The kammprofile gasket soaked for 15 minutes in potassium citrate performs as well as when soaked for 60 minutes. Therefore, waterproofing does not result in harmful gas leakage performance.

[00110] As shown by the examples above, the use of various fillers, covering a wide range of particle sizes and specific surface areas, added to the CEV in combination with a monovalent cation treatment that enhances water resistance results in an intensification of the water resistance of the filler and CEV materials combined.

[00111] Specifically, Table 3 shows that in the untreated state, 100% CEV materials have better water resistance than filled but untreated CEV materials. In contrast, Tables 4, 5, 6, and 7 show that treating the same materials as used in Table 3 with a solution containing cations that enhance water resistance surprisingly results in the CEV-filled material showing better water resistance. than 100% treated and untreated CEV material.

[00112] Furthermore, the examples show that a range of cations that enhance water resistance is suitable in the present invention.

[00113] Examples 40 to 41 refer to TH894 rings (TH894 gasket is an exfoliated vermiculite based gasket available from Flexitallic - the product is reinforced with Inconel wire).

Method and Results

[00114] The TH894 packing segments were locked in 10 mm and 45 mm diameter x-section % rings. Example 40 is a Comparative Example without any waterproofing treatment, Example 40 is subjected to 8 hours immersion in deionized water, and Example 41 is a sample treated with Potassium Citrate, immersing the % ring for 1 hour in a 0.33 M solution, subsequently washing in tap water and then drying for 2 hours at 50°C which is then also subjected to an 8 hour immersion in deionized water.

[00115] The samples immersed in water (Examples 40 and 41) were weighed before and after 8 hours of immersion; example 40 gained 53.8% weight, due to water absorption, while example 41 gained only 25.1%. Treated example 41 swelled noticeably less than untreated example 40, and did not appear as soft when removed from the water.

Example 42

[00116] A sample of TH894 was treated by coating it in a saturated solution of Potassium Citrate (3M) washing and drying as detailed for example 41. The test was again carried out by immersion in deionized water for 8 hours; swelling was intermediate between untreated example 40 and immersion treated example 41 and weight gain after immersion in water was 45.3%.

[00117] Attention is directed to all papers and documents that have been filed simultaneously with or before this specification in connection with this application and which are open to public inspection with this specification, and the contents of all papers and documents are here incorporated by reference.

[00118] All features described in this specification (including any claim, summary and accompanying figures), and/or all steps of any method or process so described, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[00119] Each feature described in this specification (including any accompanying claim, summary and figure) may be substituted for alternative features that serve the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature described is an example only of a generic series of equivalent or similar features.

[00120] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any new, or any new combination, of the features described in this specification (including any claim, summary and accompanying figure), or to any new, or any new combination, of the steps of any method or process so described.

Claims (15)

1. Water resistant sealing material, characterized in that it comprises chemically modified exfoliated vermiculite (CEV) in a proportion of 30-70% w/w sealing material and a filler in a proportion of 30-70% w/ p of sealing material, and optionally other additives in a proportion of 0-10% w/w of sealing material, wherein the modified CEV comprises monovalent cations which enhance water resistance. 2. Water resistant valve gasket or seal, the gasket characterized in that it comprises a sealing layer and optionally a core and/or backing for the sealing layer, the valve seal comprising sealing material, wherein the layer sealant/sealing material comprises chemically modified exfoliated vermiculite (CEV) in a ratio of 30-70% w/w seal coat/seal material, and filler in a ratio of 30-70% w/w seal coat. seal/seal material, and optionally other additives in a 0-10% w/w seal layer/seal material ratio, wherein the modified CEV comprises monovalent cations which enhance water resistance. 3. Valve seal, gasket or water resistant sealing material according to claim 1 or 2, characterized in that the monovalent cations that enhance water resistance are exchangeable cations and/or in which the monovalent cations that enhance water resistance in the CEV are present at cation exchange sites in the CEV. 4. Valve seal, gasket or water resistant sealing material according to any one of the preceding claims, characterized in that the monovalent cation that enhances water resistance is selected from at least one of an alkali metal, ammonia or a quaternary ammonium compound, optionally the monovalent cation which enhances water resistance is selected from one or more of sodium, potassium, rubidium, cesium, francium, ammonia, or a quaternary ammonium compound of formula R4N+ wherein R is selected from methyl, ethyl or a combination thereof. 5. Valve seal, gasket or water resistant sealing material according to any one of the preceding claims, characterized in that modified CEV levels in the seal material/layer/sheet are in the range of 30-68% w/ p of sealing material/layer. 6. Valve seal, gasket or water-resistant sealing material according to any one of the preceding claims, characterized in that at least 1% of the exchangeable cations in the gasket/valve seal/sealing layer/sealing material or leaf are monovalent cations that enhance water resistance. 7. Valve seal, gasket or water resistant sealing material according to any one of the preceding claims, characterized in that the modified CEV is at least 1% cation exchanged with monovalent cation which enhances water resistance. 8. Valve seal, gasket or water resistant sealing material according to any one of the preceding claims, characterized in that the fillers are inert fillers. A valve seal according to any one of claims 2 to 8, characterized in that the sealing material is in the form of a compression ring, optionally comprising two or more compression rings. 10. Process for producing a sealing material, characterized in that it comprises the steps of: a) mixing chemically exfoliated vermiculite (CEV) with a filler to form an intimate mixture thereof; b) optionally forming a sheet from the mixture; c) optionally drying said sheet formed from the mixture; and d) exchange of monovalent cation of the mixture/sheet/dry sheet by contacting it with a solution of the monovalent cation which enhances the water resistance. 11. Process according to claim 10, characterized in that after mixing the CEV and the filler, the intimate mixture is formed in the sheet and at least partially dried and optionally incorporated into the gasket or valve seal before the cation exchange monovalent that enhances water resistance. 12. Process according to claim 10 or 11, characterized in that the concentration of the monovalent cation solution that enhances the water resistance is in the range of 0.1 - 10 mol.dm-3. 13. Process according to any one of claims 10 to 12, characterized in that the gasket/valve sealing ring/sheet/sealing layer/sealing material is immersed in the monovalent cation solution of 0.2 - 3 .0 mol.dm-3 for a period of between 5 - 180 minutes. 14. Process according to any one of claims 10 to 13, characterized in that the mixture/sheet/dry sheet is placed in contact with a solution of a citrate or chloride salt of the monovalent cation that enhances water resistance . 15. Process according to any one of claims 10 to 14, characterized in that the monovalent cation that enhances water resistance is as defined in any one of claims 1 to 9.

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